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Pool, spa and sauna electrics.
Indoor pools, spas, saunas, steam rooms and hot tubs: designed to the Wiring Regulations, coordinated with your pool supplier, and lit to look the part.
Water, heat and electricity need careful design. Wet skin lowers the body’s resistance, so a shock that would be unpleasant elsewhere can be fatal by a pool. BS 7671, the Wiring Regulations, treats pools and saunas as special locations with their own rules, and we design to them from the first drawing.
Swimming pools and spas
Section 702 of BS 7671 divides the space around a pool into zones. Zone 0 is the water itself; zone 1 extends 2 m out from the pool edge and 2.5 m above it; zone 2 runs a further 1.5 m beyond that. What follows from that:
- Lighting in the water runs at safety extra-low voltage, no more than 12 V AC or 30 V ripple-free DC, from a transformer or driver outside the zones, with fittings rated for immersion.
- No sockets or switches in the zones nearest the water, apart from narrow exceptions. Controls go further back or outside the pool hall.
- Water-resistant equipment in each zone, rated for splashing and for hosing down where the floor is cleaned with jets.
- Supplementary bonding of metalwork in the zones, so nothing can rise to a dangerous voltage.
- Plant rooms with their own distribution for pumps, filtration, heating and dehumidification, labelled and easy to isolate.
Saunas and steam rooms
Section 703 covers rooms and cabins containing sauna heaters. Every circuit in the room needs 30 mA RCD protection (the heater itself only where its manufacturer recommends it), and cables and fittings must suit the heat where they are mounted. Steam rooms need high IP ratings and careful lighting choices. In both, we follow the heater or steam generator manufacturer’s supply instructions to the letter.
Hot tubs and swim spas outside
A dedicated circuit to the manufacturer’s specification, armoured or ducted cable, RCD protection, and a local isolator where the installer and the manufacturer need it. We plan the route before the base is laid. See garden and exterior lighting for the rest of the garden.
Lighting the pool hall
The photographs show how much the lighting does: concealed cove lighting to lift the ceiling, underwater light to bring the water to life, and pendants and planting for scale. We put it all on lighting control so the room has a swimming scene, a relaxing scene and a night scene. See smart home and lighting control.
Frequently asked questions
Is pool or sauna electrical work notifiable?
In England, a room containing a swimming pool or sauna heater is a special location under Part P. A new circuit, a consumer unit replacement, or an addition or alteration to a circuit in that room is notifiable. We certify and notify it through our scheme.
Can I have normal sockets and switches by the pool?
Not close to the water. BS 7671 divides the area around a pool into zones. Sockets and switches are not allowed in the zones nearest the pool, apart from narrow exceptions, and are placed further back or outside the pool hall.
What lighting can go in the pool itself?
Underwater lights must be rated for immersion and run at safety extra-low voltage, no more than 12 V AC or 30 V ripple-free DC, from a source outside the pool zones.
Do you install the pool, spa or sauna equipment?
No. Your pool, spa or sauna supplier provides and commissions the equipment. We design and install the electrical supply, distribution, bonding, controls wiring and lighting, and coordinate with them from the start.
How often should a pool installation be inspected?
Chlorine, humidity and heat are hard on electrical equipment, so pool halls, plant rooms and saunas benefit from more frequent inspection than the rest of the house. We can set a schedule and carry out EICRs and maintenance.
Photographs: the basement pool and spa at a private residence in Totteridge, a project led by our director Michael Simm and now maintained by SEGplc (professional photography). See more in private homes. Regulation summaries are a guide only; the full requirements are in BS 7671 and Approved Document P. Written by SEGplc. Last updated 11 October 2026.
Need it done by a date?
Tell us the deadline. We’ll tell you honestly whether we can hit it — and we usually can.